Scroll apparatus for fluid compression or expansion are characterized by two opposed interfitting spiroidal wraps, typically generated as involute spiroids about respective axes. Each spiroidal wrap is mounted on an end plate and has a tip disposed in contact or near contact with the end plate of the other wrap and each wrap further has flank surfaces which adjoin the flank surfaces of the other wrap to form a plurality of moving fluid compression or expansion chambers.
In one relatively well developed configuration of scroll apparatus, one of the scrolls is fixed with respect to a support housing and the other scroll is connected to a drive shaft, in the case of a compressor, or a power output shaft in the case of an expander, and relatively complex linkage is provided for conversion of orbital motion of the movable scroll to rotary motion of the shaft. Such mechanism includes an eccentric driving member and coupling mechanism, such as an Oldham type coupling, to permit orbital motion of the movable scroll without allowing rotation of same with respect to the machine housing. Alternatively, one of the scroll members, commonly referred to as the idler scroll, may be connected to the driving or driven scroll member through an Oldham coupling and both members are rotated to provide coaction between the scroll wraps to develop the moving compression or expansion chambers. This type of scroll apparatus is typically referred to as a co-rotating or co-rotational type.
Co-rotating scroll expansion or compression apparatus is inherently less complicated, mechanically, generates less mechanical vibration and usually generates less noise than the so-called fixed scroll type apparatus. The latter two advantages of co-rotating scroll apparatus are particularly important in applications of scroll apparatus as compressors used in commercial as well as household vapor compression air conditioning and refrigeration systems.
A significant factor in providing an efficient and mechanically reliable scroll apparatus is the assurance of proper sealing engagement between the cooperating opposed scroll wraps to prevent unwanted fluid leakage from the expansion or compression chambers. Leakage may occur at the contact lines along the flank surfaces of the cooperating scrolls as well as at the axial side edges or tips of the scroll wraps if precise dimensioning and positioning of the wraps cannot be obtained and/or forces tending to separate the scroll flanks cannot be overcome due to deflection of the machine components and machining tolerances, for example. Although contact between the scroll flank surfaces of the respective scroll wraps is desired to minimize fluid leakage, the contact force should be limited so as to minimize wear between the scroll wraps. On the other hand, it is necessary in fluid handling apparatus wherein liquid slugs may be passed through the compression or expansion chambers from time to time to allow some momentary separation of the wraps to prevent mechanical damage to the scrolls. This is particularly important in compressors used in vapor compression refrigeration systems wherein a lubricating oil is injected into the moving chambers to aid in the sealing function, to reduce compression work and to provide a lubricant for the scroll wraps and other components in the system.
Radial compliance mechanisms have been developed for so-called fixed scroll type fluid handling apparatus to overcome the above-mentioned problems in providing adequate sealing while allowing movement of the scroll wraps relative to each other to handle fluid slugs and to reduce starting torque of machines, such as compressors. However, in co-rotational scroll type apparatus it has been determined that it is more desirable to provide for limited radial movement between the driving or driven scroll and the rotating idler scroll by permitting movement of the idler scroll center of rotation or central axis with respect to the axis of the driving or driven scroll. Providing a radial compliance mechanism which allows limited movement of the center axis of the idler scroll provides a mechanically simpler and more reliable apparatus than is possible by utilizing prior art radial compliance mechanisms connected to an orbiting type driving or driven scroll. It is to these ends that the present invention has been developed.